Method of preventing corrosion of metal walls of tanks



April 9, 1935. B. BUTTERWORTH 1,995,747

METHOD OF PREVENTING CORROSION OF METAL WALLS OF TANKS Filed April 7,1953 2 sheet s-she et '1 Q .WGATTORNEY.

April 9, 1935. I A. B. BUTTERWORTH METHOD OF PREVENTING CORROSION 0FMETAL WALLS Of TANKS Filed April '7, 1933 2 Sheets-Sheet 2 #k ATTORNEN'.a

2 Patented Apr. 9, 1935 METHOD or PREVENTING coaaosron or METAL WALLS orTANKS Arthur B. Butterworth, Brooklyn, N. Y.

4 Application April 7, 1933, Serial No. 664,865

11 Claims.

This invention relates to the cheap and efficacious treatment of theexposed inner metal surfaces of tanks, more particularly the cargo tanksof vessels known as tankers, and has for 5 its particular objects theapplication tosuch surfaces of an adherent corrosion-inhibiting coatingwhich E exceedingly cheap, is adapted to be sprayed on such surfaces,'isresistant to but inert toward and therefore without effect upon gasoline19 or otherpetroleum distillates and petroleum oils ily ,and completelyremoved when it is desired to gas-free or clean such tank by a merepressure jet cleaning operation, such for example as that described inmy prior Patent No. 1,806,740.

It has long been recognized thatthe deterioration due to corrosion oftankers engaged in the transporting of gasoline and other oil distil- 20lates is a vital problem insofar as the cost of upkeep of a fleet ofsuch tankers is concerned, since the normal life of such tankers isshortened by many years as a result of such-corrosion. Many attemptshave been made to protect the inner metal walls of the tanks of suchvessels by applying thereto various coatings, either applied manually orby means of a gunsprayer manipulated by an operative stationed withinthe tank throughout the spraying operation. However, of necessity thechoice of such coating compositions was greatly restricted because thegasoline acted as a solvent for the oil vehicles of any oil paints,thereby destroying the bond of such paint with the metal, besidesbecoming contaminated by such vehicle. Furthermore, the application ofsuch paints whether applied by hand or by a hand gun necessitated theerection of temporary staging within such tank and required the presenceof one or more operatives within the tank during the entire coatingoperation. Moreover,

and objectionably thick accretions thereof tend to .form in and on thechannel irons and other braces for the walls of the tank and suchcoating does not lend itself to being readily removed from the walls ofthe tank by such tank cleaning operations as previously referred to;and, in the case of the latter type of coatings, the same are expensiveso as to render the cost of coating a large tank almost prohibitivebesides having other objectionable features. l My investigations haveled to the discovery that the inner metal walls of such tanks can besatisfactorily coated with an adhesive, corrosion-inhibiting coating,inert to gasoline, water ballast and the. like, without necessitatingthe presence of an operative within such tank, through the employment ofautomatic coating apparatus of 5 the type described in my said priorPatent No. 1,806,740 or such as the type herein described andfurthermore, that certain water paints and more particularly unslakedlime, preferably slaked in situ in the coating container, or evenordinary air slaked lime, are highly satisfactory for-this purpose.

In the accompanying drawings I have illustrated a form of automaticcoating apparatus suitable for applying a corrosion-inhibiting coatingto-the inner metal surfaces of tank walls and also have illustrated themanner in which my improved coating method is performed.

Referring to the drawings Figure l is a fragmentary elevation, partlydiagrammatic, showing my improved apparatus in, position within the tankof an oil tanker;

Fig. 2 is a fragmentary detail elevation of the nozzle-drivingmechanism; v

Fig. 3 is a vertical section, partly in elevation, of the sprayingnozzles and certain associated 'parts of the apparatus; and

Fig. 4 is a fragmentary side elevation of the construction shown in Fig.3.

Referring to the construction of the apparatus illustrated in thedrawings, the letter A designates a tanker having cargo tanks B, thelatter having side walls I, bottom 2 and top 3, The top of each tank isprovided with a man hole 4 adapted to be closed by a cover 5, thevertical flange of said man hole being apertured to receive a flexibleair hose 6 and said cover being apertured to receive a cylindricalcasing l which is tapped into the bottom'of agear box 8 wherein it isrigidly secured against rotary motion by set screws 9 or by a suitablespline. Said gear box comprises a two-piece casting, the lower half ofwhich has an integral vertical flange on' which an air-motor C ismounted, the same serving to drive a gear ll through an intermediateworm l2 carried by the motor shaft. Journals I3, l3 areprovided inthetop and bottom of the gear box, the former journal serving to receivethe hub M of said gear and the latter receiving an internal supply pipel5 which is rigidly secured to said hub and held against by means of setscrews H5, or being otherwise splined thereto. As shown, said gear I0 isalined between washers I! interposed between the resp'ective top andbottom faces of the gear and the adjacent journals of the gearbox.

Said internal pipe is threaded at its upper end into a flanged bushing25 which is rotatably mounted within an ordinary stuffing box 26 that isclosed at the top by a screw cap 21 and which 60 is laterally apertm'edto receive a, pipe nipple 28 to which the main water conduit isconnected. The top flange of said bushing normally rests on and iscarried by the shoulder 30 in said stuffing box and a set screw 3|serves to limit the upward movement of the bushing 25.

A ring gear 35 is splined by a spline 36 on the lower end of the casingI. A T 31 is threaded on the lower end of the pipe IS, the same beingprovided with a removable keeper 38 which admits of the-insertion intosaid T of a hollow sleeve 39 that is provided with a series of apertures40. Said sleeve is provided with peripheral guides or beads 4| and itsrespective ends are threaded to receive the opposing nozzles 42. A gear43 having either one less or one more tooth than the ring gear 35 iskeyed to the sleeve 39, being locked in position by a lock nut 44.

A portable stripping pump D, having a suction leg 50 that projects intoclose proximity to the low point of the tank and which is driven by abelt or chain 5| connected to an air motor F, serves to elevate theliquid coating composition that has previously been introduced into thetank, through the valve controlled return pipe 52 and delivers the sameto the supply main 29.

The said air line 6 as shown, is connected to a T' 53 from whichbranches thereof lead to the respective air motors C and F respectively.

Inorder to coat a tank with a preservative coating in accordance with myinvention, I preferably proceed as follows:-

The coating solution, which preferably comprises milk of lime is formedin situ in the tank by slaking lime with sea water in the proportion ofabout 1 "pounds of such quick lime to a gallon of water. The advantageof slaking lime in situ is the fact that the slaking reaction beinghighly exothermic generates sufficient heat to virtually raise thetemperature of the liquid to the boiling point and this heated coatingmixture is far more efiective for coating metal tank walls than a 'coldsolution, as the hot coating, when applied. under pressure dries to ahard, dense, resistant layer which is substantially unaffected byth'e'swashing of gasoline cargoes or of salt watercargoes. Preferably,moreover, the water employed for the slaking should be salt water, asthe coating prepared with saltwater also has a more effective bond withthe metal of the tank walls and is more resistant to erosion by theswashing of gasoline or other distillates or salt water ballast thancoatings prepared by slaking the lime with fresh water. Furthermore,salt water is always available. v

The aforesaid coating solution having been prepared within the tank, andthe above described apparatus having been installed within the tank asillustrated, the two air motors are caused'to operate by compressedairsupplied through the respective branches of the hose 6. The lower motorF thereupon causes the pump D, which as stated is so positioned that thesuction leg thereof projects into proximity to the bottom of the tank atthe low point thereof, to elevate the coating solution through the pipe52 to the delivery main 29 from whence it passes into the internalsupply pipe l5, thence through the T 31 into the sleeve 39 through theapertures 40 and out through the jet nozzles 42. The worm and the gearinterconnecting the shaft and air motor and the supply pipe l5 serve asa reduction gear which results in the slow revolution of the pipe l5 andthe worm gear 34 carried thereby and the T 31 mounted on the lowerBDdthGIEOf. Such revolution of the ring gear l4,-which meshes with theperpendicular gear 43, the latter preferably having one more tooth thanthe gear 34', together with the simultaneous rotating of the T 31 withsuch ring gear 34, results in the nozzles constantly changing their pathduring the rotation thereof and sweeping in a curvilinear and constantlychanging path until the jets projecting from such nozzles have impingedagainst all portions of the inner surface of such tanks within whichsuch T carrying thev nozzles is substantially centrally mounted, all inthe mannerdescribed with reference to the jet spraying apparatusdisclosed in my prior Patent No. 1,806,740. As a consequence, thecoating solution is delivered under pressure against all the surfaces ofthe tank. Preferably, I employ a nozzle pressure of less than 75 lbs.rather than in excess of 7 5 lbs. when applying the coating solution tothe tank walls, since the walls to which the coating is applied havebeen previously cleaned and scaled either by manual methods or by themethod described in my said prior patent and if excessive pressure isemployed which is more than suiiicient to cause the projection of thejets from the nozzles to the surfaces to be coated, there will be notonly unnecessary spattering of the said paint coating from suchsurfaces, but there will be a tendency for the coating to not adhere asefiectively to the surfaces as if just sufficient pressure is employedto impart to the jets suficient force to cause the same to reach everyportion of the tank within which the machine is mounted. As stated, thesurplus liquid which drains from the walls will collect at the low pointof the tank and be recirculated by the pump D through the sprayingnozzles and consequently it is only necessary to insure that suiiicientcoating solution is supplied to the leg 50 to continuously maintain aliquid seal'between .the bottom of said, leg and the tank bottomthroughout the coating operation and thereby such coating isaccomplished continuously without any halts or shutdowns being requiredto blow out the accumulated masses of solid material or residues fromthe paint solution. Furthermore, the presence of an operative in thetank is not required at any time throughout the entire coatingoperation.

At the end of the operation, any residual coating solution in the tankcan be removed by means of the pump or in any other desired manner.

In lieu of a special portable pump, a suction leg connected to theship's pump may be employed and such suction leg is then connected by apipe, such as 52, with the supply main 28.

My improved coating can be readily removed by means of hot salt waterapplied under high pressure in the form of jets in the manner describedin my aforesaid Patent No. 1,806,740 and consequently with each cleaningoperation it is possible to obtain a smooth scaled surfa'ce which isideally adapted to receive a smooth and even coating applied in themanner herein described.

If desired, a pump, such as the ships stripping pump, or even the cargopumps, located in a compartment outside of the tank to be cleaned may beemployed, and in such event, the suction side of such pump will beconnected either with the container for. the coating solution, or withthe body of coating solution. in the tank and the discharge of such pumpwill deliver into the main 29. In those cases where a number of tanksare to be coated, then the necessary piping, as here- I tanks, forexample, the pump in the fire line can.

be employed merely by suitably connecting the same so as to supply thecoating solution to the nozzles.

Preferably the coating liquid is propelled against the surface in theform of solid jets or streams as distinguished from an atomized spray,since thereby there is practically no tendency for the [nozzles tobecome clogged with solid material carried in suspension by the coatingsolution.

The application of a preservative coating in the manner herein describedto the metal walls of tank, particularly of tankers, is particularlysuitable, not only for tankers carrying cargoes of gasoline, but alsofor tankers carrying crude oil on one trip and which are intended tocarry color specification gasoline or petroleum oils on the other trip,as after the tanks have been cleaned, this buffer coating wouldconstitute'an ideal coating for the tank adapted to receive theaforesaid color specification oils.- Furthermore, where, as isfrequently the case, tankers are required to lay idle for long periods,the pre-coating of the walls of the tanks in the manner hereindescribed, tends to reduce corrosion of such tanks, during such periodsof idleness, to a minimum.

One of the especial advantages of quick lime is that it is stronglyalkaline in reaction and thereby tends to neutralize any acid oracid-reacting compounds in or on the walls of the tanks so treated,besides serving to ideally prevent corrosion, due to the fact thatcorrosion of the metal walls of such tanks does not occur, or ismaterially inhibited, where the metal surfaces are maintained whollyneutral or slightly alkaline in reaction.

Among the additional advantages, in addition to those heretofore notedthat are secured through the employment of salt water as the vehicle ofthe coating, is the fact that it is universally available for marinevessels and furthermore, that being of a considerably greater densitythan fresh water, dueto the salt content thereof, the calcium hydrate(Cami-Dz) resulting from the slaking of the quick lime (CaO) or otherinsoluble compounds employed is more uniformly held in a state ofsuspension in such vehicle.

While quick lime, because of its many advantages, is preferablyemployed,I may also employ other water paints having an alkalinereaction or capable of neutralizing any acid ingredients contacting withthe metal surfaces, even though the same'are less desirable, such otherwater paint comprising, for example, a mixture of sodium silicate (waterglass) with whiting (natural calcium carbonate). If the proportion ofwhiting to sodium silicate be reduced to say one pound of whiting to thegallon of sodium silicate, the mixture sets too quickly to besatisfactorily sprayed. However, in those cases where a coating that isespecially resistant to erosion by the swashing of salt water ballast isdesired, the surfaces of the tanks after being coated with quick limecan be given a coat of sodium silicate whereby an insoluble coating ofcalcium silicate will be formed in situ on such metal surfaces, whichcoating. also possesses corrosion-inhibiting properties to a highdegree, besides being as stated extremely resistant to the erosiveaction of ballast water.

While it isfar more satisfactory that the coating solution be projectedupon the surface in the form of solid impact pressure jets, the coatingmay be atomized with air prior to its introduction into the supply pipel and thence discharged through the nozzles 42 against the tank surfaceswhile thelatter are rotating in the man ner here- 1 in described. 5

In order that no objectionableclogging of the nozzles by the compoundssuspended therein will occur and furthermore, in order that the momentumof the jets shall be sufficient to project the coating upon all surfacesof .a tank even as large as 30' square by 30' high, the nozzle aperturesmay desirably be of about A," in diameter and a nozzle pressure of fiftypounds per square inch may be employed. One advantage of a the deliveryof solid impact jet of the coating solution upon the surfaces to becoated as distinguished from a mere atomized spray, such as obtainableby the employment of a gun sprayer, is the fact that the resultant corrosion inhibiting coating produced on the metal surfaces when dry isvery dense and has a much stronger bond, therefor, with the metalsurfaces than otherwise would be the case, with the consequence that thecoating is much more resistant to erosion by the swashing of saltwaterballast than would otherwise be the case.

As is apparent from the foregoing description of my improved method, itis feasible to project hot milk of lime, which is extremely corrosive tothe human skin and hair, against the interior walls of tanks and toeffectively coat the same without necessitating the presence of anoperative within the tank, since the path of projection of the streamsfrom the nozzles is mechanically changed by precise, predeterminedincrements of change. As a consequence, it is possible to preservetankers and storage tanks against corrosion by a remarkably cheap andeffective procedure and which protection, because of the high I in setforth may be made without departing from the spirit of my invention asembraced within the scope of the appended claims.

Having thus described my invention, what, I claim and desire to obtainby United States Let ters Patent is:

1. The method of preserving from corrosion the interior surfaces ofmetal tanks adapted to contain petroleum oils or distillates, whichcomprises applying to such surfaces a uniform corrosioninhibitingcoating, which is substantially inert to petroleum oils or distillateg,by delivering to such surfaces, from a main body of a water suspension,which is substantially free from any organic binding agent, and whosesolid content consists principally of a material selected from the groupconsisting of hydrates andcarbonates of alkaline earth metals, impactjets of such solution and while repeatedly effecting a uniform andpredetermined change in direction of the impact paths of such jets uponsuch surfaces and con-' stantly removing from the tank bottom thesurplus solution which drains off of the other surfaces of such tank andreturning the same to the main body of coating solution for reuse insuch.

coating operation.

2. The methdd of preserving from corrosion" the interior surfaces ofmetal tanks for the StO1'-,

- ing agent, and whose solid content consists principally of one or moremembers of a group consisting of the hydratesand carbonates of alkalineform change of direction of the paths of impact of such jets alongsuchsurfaces and without substantially changing the zone of delivery of suchjets into said tank.

3. The method of preserving the interior metal walls of tanks for thestoring or transporting of petroleum oils or distillates againstcorrosion, which comprises causing milk of lime to impinge in the formof pressure impact jets against the surfaces of such walls, whileeffecting a predetermined and uniform change of direction of the pathsof impact of such jets along such surfaces without substantiallychanging the'zone of delivery of such jets into said tank.

4. The method of preserving from corrosion, the interior surfaces ofmetal tanks for storing or transporting petroleum oils or distillates,which comprises directing against such surfaces pressure impact jets ofa coating mixture comprising a water suspension, which is substantiallyfree from any organic binding agent, and whose solid contents consistprincipally of one or more members of a group consisting of the hydratesand carbonates of the alkaline earth metals, which compound issubstantially inert towards petroleum oils and distillates, whileeffecting, without manual manipulation from within the tank, apredetermined and uniform change of direction of the paths of impact ofsuch jets upon such surfaces without substantially changing the zone ofdelivery of such jets into said tank or requiring the presence of anoperative therein.

5. The method of preserving the interior metal surfaces of tanks forstoring or transporting petroleum oils or distillates, which comprisesdelivering against such surface impact jets of a coating mixturecomprising a water suspension, which is substantially free from anyorganic binding agent, and whose solid content consists essentially'ofmilk of lime and while simultaneously removing the used solution at arate to maintain the bottom surface of such tank substantially bare ofsolution and in a condition to be coated by the same operation andduring such coating operation effecting the repeated uniform change ofdirection of delivery of such jets so as to cause the same tosuccessively impinge against different areas of such surfaces and toultimately impinge against every portion thereof.

6. The method of preserving from corrosion,

the interior surfaces of metal tanks for storing or transportingpetroleum oils or distillates, which comprises directing against suchsurfaces pressure impact jets of a coating mixture containing at least10% of dissolved and suspended solids whichconsist principally of one ormore members of a group consisting of the hydrates and carbonates ofalkaline earth metals, which compound is substantially inert towardspetroleum oils and distillates, while effecting, without manualmanipulation from within the tank, a predetermined and uniform change ofdirection or the paths of'impact of such jets upon such surfaces withoutsubstantially changing the zone of delivery of such jets into said tank.

'7. The method of preserving the interior metal walls of tanks for thestoring or transporting of petroleum oils or 'distillates againstcorrosion, which comprises causing milk of lime to impinge in the formof pressure impact jets against the surfaces of such walls, and thencoating such surface with a coating consisting essentially of sodiumsilicate in solution, whereby through interaction of the two coatings soapplied, a dense, hard gasoline and water resistant coating is producedon such surfaces.

8. The method of preserving against corrosion the interior metalwalls oftanks, which comprises causing the projection against the walls of saidtank from moving nozzles disposed within such a tank of a mixturecomprising a water suspension, which is substantially free from anyorganic binding agent, and whose solid content consists essentially ofone or more members selected from the group consisting of hydrates andcarbonates of alkaline earth metals, while mechanically changing thepath of projection of the streams delivered by said nozzles bypredetermined increments.

9. The method of preserving from corrosion the interior surfaces ofmetal tanks adapted to contain petroleum oils or distillates, whichcomprises applying to such surfaces a uniform corrosioninhibitingcoating, which is substantially inert to petroleum oils or distillates,by delivering to such surfaces from a main body of salt water,containing a material selected from the group consisting of hydrates andcarbonates of alkaline earth metals in suspension therein, impact jetsof such solution and while repeatedly effecting a uniform andpredetermined change in direction of the impact paths of such jets uponsuch surfaces and constantly removing from the tank bottom the surplussolution which drains off of the other surfaces of such tank andreturning the same to the main body of coating solution for reuse insuch coating operation.

10. The method of preserving from corrosion the interior surfaces ofmetal tanks adapted to contain petroleum oils or distillates, whichcomprises applying to such surfaces a uniform corrosion-inhibitingcoating, which is substantially inert to petroleum oils or distillates,by delivering to such surfaces from a main body of salt water,containing calcium hydrate in suspension therein, impact jets of suchsolution and while repeatedly effecting a uniform and predeterminedchange in direction of the impact paths of such jets upon such surfacesand constantly removing from the tank bottom the surplus solution whichdrains off of the other surfaces of such tank and returning the same tothe main body of coating solutionfor reuse in such coating operation.

11. The method of preserving the interior metal walls of tanks for thestoring or transporting of petroleum oils or distillates againstcorrosion, which comprises causing a solution containing in suspensiontherein a material selected from the group of hydrates and carbonates ofalkaline earth metals to impinge in the form of pressure impact jetsagainst the surfaces of such walls, and then coating such surface with acoating consisting essentially of sodium silicate in solution, wherebythrough interaction of the two coatings so applied, a dense, hardgasoline and water resistant coating is produced on such surfaces.-

B. BUTIERWORTH.

